This invention relates generally to the transportation and internment of spent nuclear fuel rods and, more specifically, to the assembly of fixtures used in the transportation and internment of spent nuclear fuel rods.
The safe transportation and/or internment of spent nuclear fuel rods is a highly complex task. The spent fuel rods must be rigidly retained within a structure which virtually guarantees proper spacing between the rods. Also, the structure must be extremely rugged and not apt to lose its structural integrity even in a massive traumatic occurrence, such as in a train derailment.
One such structure is illustrated in FIG. 1 and will hereinafter be referred to as a basket assembly. The basket assembly comprises a large plurality of metal disks, spaced apart by spacers and held rigidly together by parallel support rods. Defined within each of the steel plates are square apertures having dimensions which meet rigid tolerances. Each square aperture in each steel plate is carefully aligned with a square aperture in each of the other steel plates so as to form an elongate, square cross-sectioned tubular opening within the basket assembly. Thus, the basket assembly has a plurality of such elongate tubular openings. Spent fuel rods are disposed within elongate tubes having a square external cross section. The elongate tubes are manufactured to precise tolerances to perfectly fit within each elongate tubular opening within the basket assembly. As illustrated in FIG. 1, the basket assembly is capable of holding a plurality of the elongate tubes, each disposed parallel to the longitudinal axis of the basket assembly.
The basket assembly illustrated in FIG. 1 meets the rigid structural integrity requirements set by the industry and the federal government. However, the basket assembly is difficult, time-consuming and tedious to assemble. Because the tolerances between the square apertures and the elongate tubes are extremely tight, the square apertures must be aligned with considerable precision. Assembling the plurality of steel plates on the parallel support rods with such precision is extremely difficult.
Traditionally, the basket assembly is assembled vertically. The rearmost steel plate is disposed in the horizontal, threaded onto each of the parallel support rods. Spacers are placed on each of the parallel support rods and then a second steel plate is placed over the parallel support rods. The square apertures in the second plate are precisely aligned with the square apertures in the first plate. In similar fashion, each of the steel plates is assembled onto the parallel support rods, each steel plate being spaced apart from the next lower steel plate by spacers. Slowly and tediously, the basket assembly is assembled upwardly. As the basket assembly grows taller, scaffolding must be assembled around a basket assembly to allow workers to locate each new steel plate onto the parallel support rods.
During the assembly operation, maintaining the square apertures in the steel plates in near perfect alignment is extremely difficult. It is frequently necessary to disassemble a partially assembled basket assembly and begin the process of assembling the basket assembly anew.
Accordingly, there is a need for a method for assembling basket assemblies which avoids these aforementioned problems with the prior art.